The people that walked in darkness (comp. Isaiah 8:22). All the world was "in darkness" when Christ came; but here the Jews especially seem to be intended. It was truly a dark time with them when Christ came.
Have seen; rather, saw. The "prophetic" preterit is used throughout the whole passage. A great light. "The Light of the world," "the Sun of righteousness," "the true Light, which lighteth every man that cometh into the world, "first broke on man in that northern tract" by the way of the sea, "when Jesus came forward to teach and to preach in "Galilee of the Gentiles."
For thirty years he had dwelt at Nazareth, in Zebulon. There he had first come forward to teach in a synagogue (Luke 4:16-21); in Galilee he had done his first miracles (John 2:11; John 4:54); at Capernaum.
"Upon the sea coast, in the borders of Zabulon and Nephthalim," he commenced his preaching of repentance (Matthew 4:13-17). The "light" first streamed forth in this quarter, glorifying the region on which contempt had long been poured.